Many locations have substantial fixed telephone networks, which are not connected or are poorly connected with other telephone networks. As the coverage of cellular radio telephone systems grows, an opportunity arises to connect these isolated networks to other networks by the radio-telephone access service provided by cellular systems. Both large-scale and small-scale instances of the need for this exist.
A factory in a rural area, for example, which has a telephone network to facilitate communication among its employees, needs to be connected to a public telephone network. In certain areas, the cost of wired facilities to connect this factory to a switching center may be quite large. When a cellular system covers this factory, it may be less expensive to connect the factory's network to the public network by this cellular system.
As a larger example, consider an entire city in a remote part of the world. Wiring that city to the national or international network may be far more expensive than connecting it by a cellular communication system. A system that provides ubiquitous coverage using satellites which project radio coverage patterns onto the earth's surface, can be used to provide this connectivity.
In existing cellular systems, mobile radio-telephone sets (subscriber units) and related accessories have been manufactured which allow single fixed telephone sets to connect to a cellular network. Private telephone networks have allowed access to their service from other networks, and access to other networks from within. Multi-stage dialing procedures avoid having many accesses between the networks as are on either side of the boundary between them.
In existing cellular networks which use the "Global System for Mobile Communications" standards (referred to herein as GSM) for subscriber control and network behavior, no provision has been made to allow isolated networks supporting more than one fixed telephone set to access a communication network using procedures for efficient resource utilization. Further, no provision has been made to do this without using multi-stage dialing procedures. These isolated networks are generally so large that to allocate a radio access resource dedicated to each fixed telephone set would be economically and physically prohibitive.
Thus what is needed are a method and apparatus that have the characteristic that radio access resources are utilized as efficiently as possible. Moreover, what is also needed are a method and apparatus that avoids multi-stage dialing procedures and allows directory numbers of telephone sets in an isolated network to be called directly by callers in other networks.
What is also needed are a method and apparatus for providing a voice connection between a satellite communication system and networks in areas of the world that cannot support a full gateway due to poor infrastructure, lack of international switching center (ISC) interconnection and financial considerations. What is also needed are a method and apparatus for associating multiple circuits to a single mobile number within a mobile environment. What is also needed is a signaling algorithm for communication with a mobile exchange unit that associates multiple circuits to a single mobile number within a mobile environment.